The present invention relates to a thin film magnetic head suited for magnetic recording at a high density.
For the magnetic materials for constituting magnetic poles for a thin film magnetic head, Ni-Fe alloys capable of exhibiting a magnetic saturation flux density of 1 T at highest have heretofore been used. At present, however, there exists an intensive demand for increasing the magnetic saturation flux density of the thin film magnetic head material with a view to enhancing the recording density.
By way of example, a thin film magnetic head in which a non-crystalline Co-containing alloy film having a saturation flux density of about 1.4 T is employed for realizing the magnetic pole of the thin film magnetic head is disclosed in "Digests of the Seventh Annual Conference on Magnetics in Japan", 8PA5 (1983), p.117. Further, use of Fe-Si-Ru alloy having a saturation flux density of about 1.7 T for the magnetic material of a thin film magnetic head for a vertical magnetic recording is described in "IEEE Trans. On Mag.", Vol. MAG-20, No. 5 (Sept., 1984), pp. 839-841.
However, no consideration has been paid to problems encountered in the industrial-scale manufacturing process of thin film magnetic heads in which an organic material such as photoresist, PIQ (commercially available from Hitachi Kasei of Japan) or the like is used for realizing an insulating layer for electrically and magnetically insulating or isolating an upper magnetic layer and a lower magnetic layer from each other while nonorganic materials such as SiO.sub.2, Al.sub.2 O.sub.3 or the like being used for forming the gap layer, and in which the magnetic poles are realized by using amorphous or non-crystalline alloys containing Co or crystalline alloys containing Fe.
More specifically, the inventors have found that during heat treatment at a high temperature in the manufacturing process of the thin film magnetic head, an unwanted and unnecessary reaction takes place between the non-crystalline, Co containing alloy or the crystalline, Fe containing alloy constituting the upper magnetic layer and the insulating layer, to bring about deterioration in the magnetic characteristics of the magnetic pole (such as, for example, increasing the coercive force by four to five times), while a non-magnetic gap layer formed on the non-crystalline, Co-containing alloy or crystalline, Fe-containing alloy which constitutes the lower magnetic layer is separated (exfoliated) or the tendency for separation (exfoliation) is promoted in the course of high temperature heat treatment, thereby providing an obstacle in realizing the magnetic head of high quality. It has also been found by the inventors that the non-magnetic gap layer may be separated (exfoliated) from the non-crystalline, Co-containing alloy or crystalline, Fe-containing alloy constituting the upper magnetic layer, during the above-mentioned high temperature heat treatment. Parenthetically, the high-temperature heat treatment mentioned above is carried out at about 400.degree. C. for the purpose of curing the insulating layer as well as at an annealing temperature in the range of about 350.degree. C. to about 400.degree. C. for improving the magnetic characteristics of the magnetic layers.